1. Field of the Invention
The present invention relates in general to a fuel pump, and it more particularly relates to a pump for supplying liquid fuel to an engine in response to an electronic control device.
2. Description of the Prior Art
Liquid fuel pumps of the general type with which the present invention is concerned have been utilized in various industries for feeding fuel under pressure to different types of engines. A conventional fuel pump generally includes a plurality of modules such as a vapor separator, an engine-driven fuel pump, a boost pump, a pressure regulator, and a fuel control. The multi-modular arrangement increases the cost of the pump and further renders it too bulky, heavy and inaccurate for use in particular specialized applications such as in the defense and military industries.
Moreover, the foregoing problems associated with the conventional fuel pumps are compounded by the use of fuel lines interconnecting the constituent modules. Such inter-modular interconnection intensifies the concerns related to the formation of fuel vapor. Thus, the fuel pump draws in not only fuel, but also unavoidable bubbles of vapor through a suction port, or, in an extreme state, sucks only the fuel vapor so that a fuel pressure is not performed in the fuel pump. As a result, a vapor lock or flame-out phenomenon occurs and the engine stops. The fuel vapor limits the ability to accurately control the engine speed, and, therefore, renders the use of the pump undesirable in certain applications where accuracy is a prime concern such as in airborne or missile applications.
A number of unsuccessful arrangements have addressed the existing problems in the field and have attempted to improve the accuracy of the conventional pumps. Exemplary attempted techniques are disclosed in the following U.S. Pat. Nos. 4,288,983 to O'Rourke, Jr., for "Turbofan Engine Having Core Supercharging Stage"; 4,293,273 to Romanov et al., for "Axial-Flow Reversible Turbine"; 4,390,316 to Alison for "Turbine Wheel"; 4,494,560 to Napolitano, et al., for "Self-Priming System for Liquid Pumps"; 4,538,958 to Takei, et al, for "Fuel Pump Having Regenerative Section Provided With Vent Housing For Voltene Flow"; 4,538,959 to Cantor, et al., for "Clean-In-Place Pump"; 4,538,960 to Iino, et al., for "Axial Thrust Balancing Device for Pumps"; 4,545,725 to Ikeda, et al., for "Stress Corrosion Cracking Proof Steam Turbine"; and 4,588,351 to Miller, et al., for "Centrifugal-Type Air Blower Bleed Off Arrangement".
It has been known to provide a regenerative pump with a vapor vent about midway of a pump passage in order to discharge the fuel vapor out of the fuel pump. The conventional vapor vent, however, only connects the pump passage with the outside of the pump, and hence it is inevitable that a substantial amount of fuel is discharged outside of the pump through the vapor vent, even when no fuel vapor is present.